Renewable energies: let's dream with numbers

This means that the quaqntity of energy that the sun provides to the earth is 10.000 times bigger than the energy consumed every year by human activities.
Let's consider now that the medium efficiency of the photovoltaic systems used (including plant losses) is equal to 1%.
Paradoxically, if we covered the whole surface of the planet with photovoltaic panels we'd get a quantity of energy 100 higher than the annual total consumption.

So we can estimate that by using a surface equal to a hundredth of the surface of the earth we'd be able to theorically reach energy self-sufficiency.
However it would still be a very large surface, 600.000 kmq equal to about twice the surface of Italy.
This utopistic calculation is based on the hypothesis of energy consumption remaining constant.

On this issue the scientific establishment is rather divided:

• sothere are those who claims that energy consumption will grow due to the increase in population and the higher levels of general wealth

• those instead who think that energy consumption will decrease since all the technological plants used by man will tend to improve their eficiency.

On the other hand the photovoltaic system which converts solar energy into eletric energy is often taken as the only renewable source, but in many cases it is more convenient to convert solar energy into heat with a definitely higher efficiency (for instance when reheating air or water circulating in buildings).
It is much more convenient to use the sun also to naturally illuminate the environments in which we live (obviously by day) instead of using electric energy to convert it into light with a very low yield.

Solar energy is a diffused energy at low intensity and always available in the whole planet even if at different intensities: in short - little at the Poles - a lot at the Equator.
There are also other renewable sources but concentrated such as hydroelectric sources, biomasses, geothermal sources which can generate energy with very high efficiency.

If finally we add the exploitment of the wind and of the tides we can understand that reaching energy self-sufficiency with renewable sources is not such a utopic hypothesis. 
Currently in Europe the 14.3 % of the energy produced comes from renewable sources, of which 14.2 % of hydroelectric type, while only the remaining 0.1 % is generated by photovoltaic and eolic sources.    

According to recent studies done by important research institutes, in Europe there is the technical and economic possibility of of reaching by the year 2005 the 50 % of the energy production through renewable sources. 
The main obstacles to be overcome in order to reach this goal, are the little determination by governments to adopt effective politics in support of the renewable sources, and the hostility of the oil companies which fear losing power and market.

It's not by chance that the main companies producing photovoltaic cells have been bought just by oil corporations.
The sun is not only a renewable and clean source, it is also democratic, because it belongs to everybody, because it's free and no one can control its output by closing the faucet if we don't pay the bills.